Preparation And Properties Of Supported Mn-Ce-based SCR Catalysts Containing Titanium Blast Furnace Slag As Carrier

Ti-bearing blast furnace slag,a by-product of metallurgical industry,has very high potential value.Nowadays,millions tons of the slag was produced every year in China.The slag has not been efficiently utilized so far.Mountains of the slag was underused and piling up which could cause many environmental issues.The major components of the slag are TiO2,SiO2 and Al2O3,which account for 24%,19%and 15%,respectively.Above all,the slag has many similar characters with common catalyst carriers(TiO2,Si02,Al2O3,molecular sieves)used in selective catalytic reduction(NH3)of NOx by NH3.In this dissertation,a novel SCR DeNOx catalyst with manganese oxides supported by Ti-Bearing blast furnace slag was developed and systematically investigated.Firstly,Mn/Slag and ceria modified Mn/Slag catalysts were reaserched.From activity tests and characterization results,it was found that it was viable to use the slag as carriers and Ce doping could greatly enhance the SCR activity of the catalyst.The NO conversion of Mn/Slag catalyst could remain upon 80%from 180-260?with 15-30%MnOx loaded while the acive temperature window of Mn-Ce/Slag catalyst was 160-260?.The best molar ratio of Mn/Ce was 5.The surface properties,the oxygen storage capacity and the surface acidity of the Mn/Slag catalyst were improved by the introduction of Ce,which would be beneficial to the adsoroption of NH3 and its activitation.Secondly,based on the optimized Mn-Ce/Slag catalyst,several transition metals(Fe,Cu,Co,Ag)were chosen to be doped into the catalyst.According to the results of activity and characterization tests,Fe and Co doping could greatly enhance the SCR activity of the catalyst while Ag doping suppressed its activity and Cu doping had no obvious influences.BET tests results suggested that all the catalysts were in form of mesoporewhich was good for gas adsorption.XRD results showed that Co modified catalyst had the strongest reaction between Mn-Ce and the slag.XPS results outcame that Mn4+ and Ce4+ oxidation states are predominant.H2-TPR results suggested that Co was good for redox process.NH3-TPD results suggested that the surface acidity of all the catalysts but that of Ag modified catalyst was too strong to NH3 desorption.Furthermore,the operating parameters were investigated,including diameters of the slag,the calcination temperature,NH3 and O2 concentratoin.The opitimized parameters were as follows:15-25%MnOx loaded,5 of molar ratio of Mn/Ce,calcining at 500?,7%O2 and 2 of[NH3]/[NO].Finally,the effects of SO2 on the SCR activity of Mn-Ce/Slag catalyst as well as its mechanism were investigated detailedly.A serious deactivation by SO2 was detected on the catalyst.The sulfation of catalyst carriers was proved to be the main reasons for the catalyst deactivation.